Pumps and motors



July 17, 1956 c. S. PRENDERGAST PUMPS AND MOTORS 2 Sheets-Sheet l Filed March 5, 1954 70 movement 0f Roto/.9 //7 degrees Ang By 1 l Attorney July 17, 1956 Filed March 5, 1954 C. S. PRENDERGAST PUMPS AND MOTORS 2 Sheets-Sheet 2 (Sim/9 2 Inventor United States Patent ce PUMPS AND MOTORS Charles Scott Prendergast, Easlling, England,4 assignorV of one-half to Hamilton yGordon, Weyburn, Elstead, Surrey, England Application March 5, 1954, SerialrNo. 414,422 1 Claim. (Cl. 103-4) This invention relates broadly to pumps and motors and more particularly to an improved rotary pump or motor of the kind havingeaseries of stator chambers, a series of phase-displaced rotors one in each stator `chamber, and movable abutments between -the stator4 chambers and the rotors, an'd wherein the -stator chambers and the rotors are relatively proliledtobring about reciprocal rates of acceleration and deceleration of the movable abutments as the rotors rotate, whereby the total instant fluid displacement of fthe series is practically uniform. l

One of the objects of the invention is to provide .-a construction of rotary pump ormotor havingahigh degree of etliciency and reliability.

.Another object yof theL invention isto provide a` construction of rotor for rotary pumpsor motors which is formed on predetermined contours including interconnected curves, one portion of which operates in coaction with associated parts of the rotor,pump oramotor` at. a predetermined rate of acceleration, which may .beconstant, and another portion of which operates iinassociation with the saidparts of` the rotarypump ormotoreat a reciprocal rate of deceleration.

A further object of the inventionis to ,provide al new and improved rotary pump or motor, of the movable abutment type, comprising a. series of stator chambers with a series of rotors phase-displaced, there being one rotor to each stator chamber, and movable abutments, diametrically opposed, contained .between each stator chamber and rotor, inlet and discharge ports on either side of each abutment being isolated from each other by sealing contact of the abutments with the stator and rotor.

This invention is a developmentof that disclosed in the specification of U. S. Patent 2,609,754, and a further object is to modify and vadapt the principle of that patent specification to provide a device of the class described in which the perimeter of eachrotor is formed with an even number not less than four of equal arcs ofsmajor radius and with a corresponding number of equal arcs of minor radius, each arc of major radius joined-tocan adjacent arc of minor radiusbya curve detern'iined-according to mathematical formulaeforfinsuring mass'pro* duction of the rotors at relatively low cost and 'forbtaining reliable and uniform operation of pumps or motors in a large production program as set forth more fully in the specification hereinafter-following by reference to the accompanying drawings, in which:

Figure 1 is a vertical longitudinal sectional view-through a fragmentary portion of a multiple'chamber pump embodying the invention, the View being taken on' line`I-I of Fig. 2; Fig. 2 is a transverse sectionalrviewltaken on the line IIII of Fig. 1; Fig. 3 is a transverse sectional view taken on'line IIL-lll ofFig. l; Fig-#tis a fragmentary longitudinal sectional view taken on line IV-IV of Fig. 2; Fig. 5 is a fragmentary longitudinal sectional Aview taken on the -line V-V of Fig. 2; Fig. '6 isa View of oneof the identical rotors in the 'rotary'pumpfor motor in thisinvention; Fig. 7 isacurve diagramillustrating the compounded llow displacement controlled by the rotors of the rotary pump ,or motor illustrated in "Figs, 1-6 and'Fig; 8 is a 'diagram' showing the manner of 2,754,762 Patented `luly 17, 1956 laying out thecurve contours for thev rotor in accordance Awith the'principles of the invention.

:Referringto'Figs l to'reference character `1.indicates a'shaft journalledin'end housings Zand 3 ofthe -`lluid'ca'siug, the shaft having keyed thereon in theillustrated embodiment twosimilarrotors 4 (of special profile hereinafter particularly'described) phase-displaced at 90 Vdegrees and surrounded by stator elements 5. Spacer 'plate 6 separates onestator and rotor from the other stator and rotorwhile the housing members, which include liners 7, contain them at theends. The described parts are held assembledbybolts"i9,shown in the'cross sectional views Figs. 2 and 3,'but omitted from the longitudinal sectionalviews for thesake of clearness which vpass through holes formed through the end housings "2, 3, the liners? land stator'element', and the spacer.

Thebore of each stator element'is cylindrical inshape.

EachzofV the" two stator elements'has two diametrically opposed abutments l0 which slide in radially extended Vrecesses -11 in thestator elements, the recesses in one stator'coinciding radially and circumferentially with the recesses in the'other stator and disposed in a plane extend- "through the spacer'member. iSlots. 12 inthe rear of the Aabutments connect the 'outer endsof the recesses' to the bore 'of the stator. These sliding abutments bear constantly on the perimeters of .therotors under fluid pressure ontheirbuterend surfaces. Owing to the special form ofithe phase=displaced rotorsthe'luidjpressure remains 'constant' as the' uid displaced byone pair of abutments moving'outwards isat' all'timesexactly absorbed by the aligned pair of. abutments' moving inwards, by means of holeslfZA in the spacer plate 6. lnitialpressure at'the outer en'ds of' theqabutments is obtained through slots 12 inithe-rear ofthe'abutments '10. If desired slots 12 can be omitted as initialy pressure can be obtained through thesliding clearancealloweditor the abutments in the recesses.

V"Extending diametrically into theendhousing member 3 is a uidinlet duct 13 'shown more particularlyin Figs. Z'and 4 "which communicates withtwo sets of aligned holesin thesaid end member 3,` the liner '7, the stators5,:and.the`spacers`6, these alignedholes forming twodiametrically opposed fluid inlet passages 14 each of 'whichopens' radially into'the stator chambers in advance of the 'slifding'abutmentsin respect to the rotation of the shaft 1. Also .extending diametricallyinto Vthe`housing member 3, as shown in Figs. 2 and 5, isv a llui'd vdischarge 'duct 15 which communicates with'two diametrically opposed VAfluid outlet passages 16 each of which communicates radially with the stator Chambers in the rearLof theslidingabutments.

It will be understood ithat sinceeach rotor '4.coacts withe two slidingrabutmentsltl, each ofwhich is Vdisposed between a fluid inlet 14 and a Huid outlet 16, two identical displacement capacities are afforded in each stator, each ofwhichfcapacities is swept twice during oneI revolution of the rotor. Such an arrangement has the `advantage thatfit automaticallyprovides hydraulic balance of each rotor. and'consequen'tly ofthedriving shaft.

The perimeter of each rotor is formed by foar or a greater equal number of major and minor arcs, as shown .at a and b in Fig. 6, all arcs being subtended by equal of the major arcs by a predetermined amount, this amount being a governing factor in the cubic capacity of the pump or motor. The radius of a joining curve at the point mid-way between adjacent major and minor arcs is the mean of the radius of the major arc and the radius of the minor arc. The radii of the remainder of the joining curve can be determined as follows: The difference between the radius of a major arc and any radius of the joining curve between the adjacent end of the major arc and the mid-way point of the joining curve varies with the square of the angle contained between the radius and the junction point of the joining curve and the major arc. For example, if this difference is D at one degree from the end of the major arc, it should be 4 D at two degrees from the end of the major arc, and 9 D at three degrees from the end of the major arc. The difference between any radius r of the joining curve and the radius of a minor arc between the midway point of the joining curve and the adjacent end of the minor arc varies with the square of the angle contained between the radius r, and the radius at the junction point of the joining curve and the minor arc. For example, if this difference is d at one degree from the end of the minor arc, it should be 4 X d at two degrees from the end of the minor arc and 9 d at three degrees from the end of the minor arc. If this is followed in profiling the rotors 4, the abutments 10 in contact with the rotors will travel outwards for the first half of their movement at a constant rate of acceleration and for the second half of their movement at a constant rate of decleration. During the same periods the aligned abutments in contact with the other rotor will travel inwards for the first half of their movement at a constant rate of acceleration and for the second half of their movement at a constant rate of deceleration. These exactly reciprocal rates of movement determine that the uid displacement of an abutment when moving outwards is at all times equal to the fluid absorption of an abutment moving inwards, thus ensuring continuous contact at all tirnes between the abutments and the rotors. Having provided continuous contact between the abutments and the rotors by this form of profile it is found that the combined instant displacement produced by rotation of the two complementary rotors is practically constant.

Fig. 7 shows the characteristic curves for the compounded ilow of two coacting rotors.

In Fig. 8 we have shown the manner of laying out the contour of the rotor and the proportions for the several curves whereby the ends of the major circular arc and the minor circular arc are interconnected by curves which effect a constant rate of acceleration for one half of the movement of the coacting abutment and a constant rate of deceleration for the second half of the movement of the abutment. The proportions have been represented in Fig. 8 and are as follows:

A=angular length of each circular arc in degrees R=radius of major circular arc n=the number of major arcs, or the number of minor arcs r=radius of minor circular arc Rm=radius at 45 degress to a radial line bisecting either adjacent circular arc RL=radius at L degrees from end of major circular arc rL=radius at L degrees from end of minor circular arc.

The following equations govern the proportions in which the contours are formed:

I have found that mathematical formula set forth herein highly practicable in producing efficient pump and motor equipment. I realize however, that modifications may be made and I desire that it be understood that no limitation upon the invention are intended other than may be imposed by the scope of the appended claim.

The phase displacement of the rotors in series is determined by 3-6-(2 degrees I claim:

A device of the class described comprising a casing for fluid including a series of stator chambers, a shaft extending therethrough, a series of profiled rotors phase displaced degrees on said shaft, there being one rotor to each chamber aligned with the plane of the respective chamber, a division plate between said chambers, inlet and outlet passages for directing iluid through said casing and said division plate and said chambers, diametrically disposed slidable abutments extending from the casing through the stator chambers to the exterior peripheral faces of said rotors, said rotors each having its lperiphery formed on an even number not less than four of equal arcs of major radius and a corresponding number of equal arcs of minor radius, each arc of major radius being joined to an adjacent arc of minor radius by a curve determined by points located according to the equations:

wherein A=angular length of each circular arc in degrees R=radius of major circular arc r=radius of minor circular arc Rm=radius at 360 degrees to a radial line bisecting either adjacent circular arc RL=radius at L degrees from end of major circular arc rr=radius at L degrees from end of minor circular arc L=distance in degrees from end of major and minor circular arcs n=number of major arcs or the number of minor arcs.

References 'Cited in the tile of this patent UNITED STATES PATENTS 1,348,103 George July 27, 1920 2,492,687 Dall Dec. 27, 1949 2,609,754 Prendergast et al. Sept. 9, 1952 FOREIGN PATENTS v29,195 Great Britain 1912 

